Losing Body Fat

By Dietitian, Juliette Kellow BSc RD

Q: I weigh less than I have for a long time but my body fat has been lower in the past. Surely if I’m at my lowest weight, I should expect to have the least amount of body fat. Can you explain why this isn’t the case?

It sounds as though the proportion of fat and muscle in your body has changed over time. When your body fat was lower but you weighed more, it’s likely you had a higher percentage of lean tissue (muscle).

The more muscle you have, the heavier you will be. It’s why professional athletes or body builders often appear to be overweight according to the Body Mass Index classifications, even though they have a very low percentage of body fat.

In order to achieve your lowest weight, it looks as though you might have lost a lot of muscle as well as fat.

This is usually the result of a very low calorie intake – effectively, your body goes into ‘starvation mode’ and starts using your muscles to supply it with calories rather than using its fat stores, which it tries to protect at all costs.

This is a worry, especially if you’re trying to lose weight, because the amount of muscle you have in your body helps to determine your metabolic rate. Consequently, when muscle mass is reduced, your metabolic rate lowers with the result that you need fewer calories to maintain your existing weight – and therefore fewer calories to lose weight.

Without having any details about your percentage of body fat or lean tissue it’s hard to make specific recommendations, but as a guideline, women should aim for 23 to 28 percent body fat.

In the meantime, doing more exercise will help to increase the amount of muscle you have.

For best results, do a combination of aerobic activities to burn fat and resistance training to build muscle. Having more muscle might mean you end up weighing slightly more, but it’ll give your metabolism a boost so that you can eat slightly more in order to maintain your weight.